This invention concerns a micromonochromator and a process for making it.
It is applied in particular to:
wavelength multiplexing and demultiplexing in the field of optical telecommunications, and
spectrometry.
It is known that a micromonochromator includes means of diffraction associated with at least one entry point and at least one exit point.
These means of diffraction may be made with a diffraction mirror or a microguide network (phase-array) for example.
For spectrometry applications, a micromonochromator is used to measure variations in intensity on several wavelengths by sweeping several wavelengths by the means of diffraction.
To do this, the means of diffraction are turned and/or the exit point associated with a continuous photodetector is swept by a slit.
With regard to known micromonochromators including several entry points and/or several exit points, the following document can be consulted:
Microspectrometer system based on integrated optic components in polymers and spectral detection system for the VIS- and NIR range, C. Muller, O. Fromhein, J. Gottert, T. Kuhner, J. Mohr, Proc. 7th. Eur. Conf. on Int. Opt. (ECIO ""95), Th A2, Applications of Integrated Optics, p. 491 to 494.
In the case of multiplexing/demultiplexing or spectrometry, these points are positioned from the outset in a fixed manner, which, particularly in the case of spectrometry, does not allow for continuous measurement.
The purpose of this invention is to correct these drawbacks.
The micromonochromator, the subject of this invention, allows for continuous sweeping of the wavelength and not just discrete spectral measurement as was the case with the prior art.
This allows for improved spectral resolution of microspectrometers.
In the area of multiplexing, the micromonochromator of this invention has the advantage of allowing for adjustment of the central wavelength of a multiplexer after manufacturing of this micromonochromator.
In addition, during multiplexing this micromonochromator allows for free commutation on the desired transmission channel.
The micromonochromator of this invention is preferably made by any integrated optic technique (in particular for making continuous wavelength micromonochromators and mobile microguides).
Such a technique allows for collective manufacturing of micromonochromator components.
The invention applies to both multimode and monomode guide structures.
Precisely, this invention concerns a micromonochromator formed on a substrate and including means of diffraction associated with an entry including at least one entry point and an exit including at least one exit point, this micromonochromator being characterised in that it also includes:
mobile means for light guidance associated with this entry or this exit or both, the mobile means of light guidance including at least one mobile beam integrated in the substrate and equipped with at least one light guide, this mobile beam being apt to sweep the entry and/or the exit in a continuous manner, and
means for recovery to recover the light supplied by this exit.
In the case of multiplexing/demultiplexing, these means of guidance allow for optimisation of the positioning of the various entry/exit points and, in the case of spectrometry, they allow for continuous measurement.
According to a particular mode of manufacturing, the mobile beam is associated with the entry and equipped with a source of light installed directly on this beam.
The means of recovery could include photodetection means to detect the light supplied by the exit or the means of light guidance (which could be fibre optics).
The mobile means of light guidance could include a first mobile means of light guidance associated with the entry of the micromonochromator, and a second mobile means of light guidance associated with the micromonochromator exit, the first and second mobile means of light guidance including respectively at least a first mobile beam integrated in the substrate and equipped with at least a first light guide, this first mobile beam being apt to sweep the entry in a continuous manner, and at least a second mobile beam integrated in the substrate and equipped with at least a second light guide, this second mobile beam being apt to sweep the exit in a continuous manner.
This allows for making a multiplexer/demultiplexer apt to recover or transmit information in series or to make a spectrometer having a larger range of measurement than the known spectrometers mentioned above.
According to a first particular mode, the first and second beams are independent of each other. According to a second particular mode, the first and second beams are rigidly attached to each other.
According to a particular mode for making the micromonochromator of the invention, it includes several mobile beams associated with the entry and/or the exit, these beams being independent of each other at the entry and the exit respectively.
According to another particular mode, the micromonochromator includes several mobile beams associated with the entry and/or the exit, these beams being rigidly attached to each other at the entry and exit respectively.
If the means of recovery include means for photodetection intended to detect the light supplied by the exit, these means of photodetection can include means for transferring light and a photodetector arranged facing one end of the means of transfer or simply at least one photodetector.
This photodetector may be placed directly on the mobile beam, which is then associated with the exit.
The means of transfer mentioned above include for example at least a light guide or a fibre optic or a lens.
According to a first particular mode for making the micromonochromator of the invention, the means of diffraction include a mirror with multiple facets also called a xe2x80x9cstep gradingxe2x80x9d.
The positions of the facets can be calculated by the method described in the following document:
(1) French patent application No. 86 18434 of Dec. 31, 1986 corresponding to EP 0 275 795 A and to U.S. Pat. No. 4,786,133 A.
According to a second particular mode, the means of diffraction include a network of light microguides also called xe2x80x9cPHASARxe2x80x9d.
The following document may be consulted on this subject:
(2) PHASAR-based WDM-devices: principles, design and applications, Meint K. Smit and Cor van Dam, IEEE Journal of selected topics in quantum electronics, vol. 2, no. 2, June 1996, p. 236 to 250.
The present invention also concerns a process for manufacturing the micromonochromator of the invention, characterised in that the means of diffraction and the mobile means of light guidance are manufactured by an integrated optic technique.
Advantageously, they are manufactured collectively by this integrated optic technique.